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Questions and Answers
What method would you use to check if a given path is a file in Python?
What method would you use to check if a given path is a file in Python?
- os.path.checkfile(file_path)
- os.is_file(file_path)
- os.verify_file(file_path)
- os.path.isfile(file_path) (correct)
Which function returns the last modified time of a file?
Which function returns the last modified time of a file?
- os.file_mod_time(file_path)
- os.path.getmtime(file_path) (correct)
- os.access(file_path, os.LAST_MODIFIED)
- os.last_modified(file_path)
If you want to create a new directory in Python, which function should be used?
If you want to create a new directory in Python, which function should be used?
- os.mkdir(directory_name) (correct)
- os.directory_create(directory_name)
- os.create_dir(directory_name)
- os.new_directory(directory_name)
To determine if a file is readable, which method should be applied?
To determine if a file is readable, which method should be applied?
What is a correct way to obtain the size of a file in Python?
What is a correct way to obtain the size of a file in Python?
What is the main purpose of an underlying system call when reading a file?
What is the main purpose of an underlying system call when reading a file?
What will happen if you use the read method until the end of a file?
What will happen if you use the read method until the end of a file?
What is the primary effect of using the 'with' statement when opening a file?
What is the primary effect of using the 'with' statement when opening a file?
How should the Python code be modified to read an entire file in chunks of 100 characters?
How should the Python code be modified to read an entire file in chunks of 100 characters?
What type of value is returned by read calls when the file is fully read?
What type of value is returned by read calls when the file is fully read?
What does the seek pointer do during file reading?
What does the seek pointer do during file reading?
When using the read method multiple times, what does the last call return?
When using the read method multiple times, what does the last call return?
What will occur if the read method repeatedly reads more than available in the file?
What will occur if the read method repeatedly reads more than available in the file?
Which operation would you perform to create a new file in Python?
Which operation would you perform to create a new file in Python?
What is the purpose of checking if a file exists before deleting it in Python?
What is the purpose of checking if a file exists before deleting it in Python?
What is the primary use of the 'with' statement when opening files in Python?
What is the primary use of the 'with' statement when opening files in Python?
Which of the following is NOT a primitive file operation mentioned?
Which of the following is NOT a primitive file operation mentioned?
What does the 'os.remove()' function do?
What does the 'os.remove()' function do?
How would you check if a file exists before performing an operation on it?
How would you check if a file exists before performing an operation on it?
Which file operation can be completed using the 'seek()' function?
Which file operation can be completed using the 'seek()' function?
What is the likely outcome if you try to delete a file that does not exist?
What is the likely outcome if you try to delete a file that does not exist?
What does the 'with' statement help with when writing code?
What does the 'with' statement help with when writing code?
In sequential access to a file, the seek pointer begins at which byte of the file?
In sequential access to a file, the seek pointer begins at which byte of the file?
Which of the following statements is true regarding random access in files?
Which of the following statements is true regarding random access in files?
What is the purpose of the 'seek' method in file handling?
What is the purpose of the 'seek' method in file handling?
How can you copy the contents of one file to another using Python?
How can you copy the contents of one file to another using Python?
What happens when you use file mode 'r+b' while opening a file?
What happens when you use file mode 'r+b' while opening a file?
Which of the following code snippets correctly writes a string to a text file?
Which of the following code snippets correctly writes a string to a text file?
What is the result of writing to a position in the file using the 'seek' method?
What is the result of writing to a position in the file using the 'seek' method?
Flashcards
Creating files in Python
Creating files in Python
Python code can create new files using the 'open()' function in write mode ('w').
Deleting files in Python
Deleting files in Python
Python's 'os.remove()' function deletes files, but first check if the file exists with 'os.path.exists()'.
File path in Python
File path in Python
A file path specifies the location of a file on the computer's file system.
'with open(...) as ...:' statement
'with open(...) as ...:' statement
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File primitives
File primitives
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Python's 'os' library
Python's 'os' library
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File attributes
File attributes
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File operations
File operations
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Python os.path.isdir
Python os.path.isdir
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Python os.path.isfile
Python os.path.isfile
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Python os.path.getsize
Python os.path.getsize
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Python os.access
Python os.access
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Reading file metadata
Reading file metadata
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Reading file chunks
Reading file chunks
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File read method
File read method
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Seek pointer
Seek pointer
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File exhausted
File exhausted
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Closing a file
Closing a file
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with statement (files)
with statement (files)
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File read return value (-1)
File read return value (-1)
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File writing with 'with' statement
File writing with 'with' statement
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Sequential file access
Sequential file access
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Random file access
Random file access
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Seek pointer in files
Seek pointer in files
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File object method seek
File object method seek
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Writing to a specified file position
Writing to a specified file position
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Combining read and write operations
Combining read and write operations
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Chunking in files (iter)
Chunking in files (iter)
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Study Notes
OS Week 7 - Lab: File Primitives (Python)
- Introduction: The lab illustrates file operations in Python, building on concepts from week 7 lecture slides on file systems. Ten primitive file operations are covered: create named file, delete named file, open named file, close a file, read from open file, write to open file, seek in open file, get attributes of file, set attributes of file, rename a file. The lab emphasizes linking these Python operations to underlying system calls using
osandshutillibraries.
Creating Files (Experiment 1)
- Python code: Example Python code creates two text files (
tweedle-dum.txtandtweedle-dee.txt) in the current directory usingosmodule. File paths can be explicitly specified, including full paths, (e.g.,C:/Users/elboghdt/Desktop/Python/).
Deleting Files (Experiment 2)
- Python code: Example Python code uses
os.path.exists()to check if files exist before removing them withos.remove().
Opening Files
- Concept: Programming languages use explicit "open" calls to read/write files, either direct system calls, or system interfaces. These calls retrieve file metadata from the disk, then load this into data structures maintained by the OS.
Reading Files (Experiment 3)
- Purpose: Recreate
tweedle-dum.txt, add text, and read the first 100 characters. Example text provided for insertion. Additional Python Example in the notes offers a way to add file content directly.
Experiment 4: Reading Entire Files
- Python Code Example: The lab demonstrates reading and printing an entire file's content in chunks of 100 characters, using a
whileloop that reads and prints content until reaching the end of the file; or just usefile.read().
Closing Files
- Importance: The
withstatement automatically closes files after use, regardless of errors. Thiswithstatement approach is recommended for safer file management.
Writing to Files (Experiment 5)
- Purpose: Write a string to
tweedle-dee.txt.
Experiment 6: Copying File Contents
- Content: Combines reading and writing files to copy
tweedle-dum.txtdata totweedle-dee.txt
Seeking a Files / Random Access (Experiment 7)
-
Concept: Sequential access, default for files, where the operating system pointer moves to the next byte. Random access allows reading or writing at any position in the file, regardless of prior access points.
-
Python Example: Shows code using
seekto accomplish random file access.
Experiment 8: Writing to a Random Position
- Purpose: Demonstrates writing to a file at a specific random position
Getting Attributes of a File (Experiment 9)
- Purpose: Demonstrates displaying file attributes like size, last modification time.
Additional Exercises
- Exercises: Setting attributes, renaming files, directory manipulation (using
os.mkdirandos.listdir), and recursive file copying (usingshutil.copytree) are included as suggested exercises.
Reflection Question
- Task: Try to relate Python operations to the underlying POSIX system calls, using provided links.
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